Same one as trout linked to but with a link that works this time 😉 http://www.screwfix.com/p/pry-bar-203mm/37748
Screwing them down is not guaranteed to work though, it could just as easily be the joists themselves or noggings between them creaking, I’ve even traced creaking to the nails holding down the stud walls in the past.
If it doesn’t work then you’ll want to lift the offending piece, a la big phils advice but re-lay it on expanding glue. (for what its worth all new chipboard floors I lay now are on expanding glue, never had a problem with creaking since.)
Tbh though initially I think I’d punch the nails in further to increase their hold on the boards then screw right at the side of them as per chickenmans advice, this seems to work about 80% of the time, makes the nails a tad more difficult swine to remove after if you do have to take the board up though, good luck, creaking floors can be a biatch to fix!